The Diamond Maker is an old man who lives beneath the Royal Palace of Phreex. He is a tall man with whiskers like a billy-goat, and is good-natured and generous.
History
The Diamond Maker once lived in the outside world, but when he claimed to have succeeded in making diamonds, he was sent to the Isle of Phreex. There he set up a number of machines in a circular chamber below the Royal Palace, lit by electricity.
He gave John Dough three large diamonds as a gift, since his ability to produce the gems makes them less valuable to him. (John Dough and the Cherub)